For proper grammar, think about how you’re using the words which vs. that.
Essential or Nonessential
Generally, the word which introduces a clause that is not essential to understand the meaning of the sentence (nonessential) and can be set off with commas. The word that generally introduces an essential clause, which is needed to understand the sentence. A vampire might demonstrate the difference this way:
Blood that dripped freshly to his lips excited him more.
[blood dripping as opposed to some other method excited him]
The blood, which dripped freshly to his lips, renewed his strength.
[the blood renewed his strength and happened to be dripping]
Which vs. That: Academics Often Misuse Them
Often, people mistakenly use the word which in the attempt to sound more academic or in thinking it is the more proper usage. It isn’t. In choosing which or that, remember, if what follows the word is needed to understand the sentence, use that. If not, you can probably set it off with commas and use which.
A Few Other Uses
Following a preposition, use the word which, as in the following example:
The blood, for which the vampire had risked her freedom, did nothing to quell her appetite.
The blood, in which the vampire now basked, did nothing to quell her appetite.
but
The blood that flowed did nothing to quell her appetite
For more commonly misused words and phrases: https://patriciaesposito.com/wp-admin/post.php?post=180&action=edit